For example, a tapered roller bearing 1 such as illustrated in FIG. 35 is assembled in the rotation support section for a rotating shaft that rotates while supporting a large radial load and thrust load, such as the pinion shaft of a differential gear for example.
The tapered roller bearing 1 of a first example of conventional construction comprises an outer ring 2 and inner ring 3 that are arranged so as to be concentric with each other, a plurality of tapered rollers 4 and a retainer 5. The outer ring 2 has a partial tapered concave shaped outer raceway 6 formed around the inner circumferential surface. The inner ring 3 is located on the inner diameter side of the outer ring 2, and has a partial tapered convex shaped inner raceway 7 formed around the outer circumferential surface. A large-diameter side flange section 8 is formed around the end section on the large-diameter side of the outer circumferential surface of the inner ring 3, and similarly a small-diameter side flange section 9 is formed around the end section of the small diameter side so that each of the flange sections 8, 9 protrude outward in the radial direction from the inner raceway 7. Each tapered roller 4 is located between the outer raceway 6 and inner raceway 7 so as to be able to roll freely, with the end surface (head section) 10 on the large-diameter side each facing the inside surface 11 in the axial direction of the large-diameter side flange section 8. Moreover, a retainer 5 holds the tapered rollers 4.
The retainer 5 comprises a ring-shaped large-diameter side rim section 12 and ring-shaped small-diameter side rim section 13 that are concentric with each other and spaced apart from each other in the axial direction, and a plurality of column sections 14 that span between these rim sections 12, 13. The portions that are surrounded by the perimeters of these rim sections 12, 13 and a pair of adjacent column sections 14 form pockets 15 for holding the tapered rollers 4 so as to be able to roll freely. The retainer 5 that is illustrated in FIG. 35 is formed by bending metal plate, and the overall rigidity is maintained by forming an inward-facing flange shaped bent plate section 16 that is bent inward in the radial direction from the end section on the small-diameter side.
FIG. 36 to FIG. 38 illustrate a second example of a conventionally known tapered roller bearing 1a in which a retainer 5a having a different shape is assembled. This retainer 5a is formed into a single piece by injection molding of synthetic resin, or by cutting of a metal material. The basic construction is the same as the retainer 5 that was assembled in the first example of conventional construction, and comprises a ring-shaped large-diameter side rim section 12a and ring-shaped small-diameter side rim section 13a that are spaced apart from each other in the axial direction, and a plurality column sections 14a, with the portions that are surrounded by the perimeters of these rim sections 12a, 13a and a pair of adjacent column sections 14a forming pockets 15a. In this example, the rigidity can be sufficiently maintained by the rim sections 12a, 13a themselves, so differing from the first example of conventional construction, there is no bent plate section formed on the retainer 5a. Moreover, a circular concave section 20 is formed in the center section of the end surface on the large-diameter side of the tapered rollers 4a. 
In the case of either construction, as the tapered roller bearing 1, 1a operates, the tapered rollers 4, 4a tend to displace toward the large-diameter side of the partial tapered concave shaped outer raceway 6 and partial tapered convex shaped inner raceway 7 due to a large radial load that is applied from these raceways 6, 7. As a result, during operation of the tapered roller bearing 1, 1a, as the outer ring 2 and inner ring 3 rotate relative to each other, the end surfaces 10 on the large-diameter side of each roller 4, 4a is caused to rub against the inside surface 11 in the axial direction of the large-diameter side flange section 8, and the rollers 4, 4a rotate and revolve. In this case, the state of friction between the end surfaces 10 on the large-diameter side of the rollers 4, 4a, and the inside surface 11 in the axial direction of the large-diameter side flange section 8 is mainly just a state of sliding friction, so from the aspect of maintaining the wear resistance and resistance to seizure, it is a very severe condition. Therefore, conventionally, construction is such that a sufficient amount of lubrication oil is supplied to a rotation support unit in which the tapered roller bearing 1, 1a is assembled, and a sufficient film of lubrication oil is formed between the sliding surfaces of the end surfaces 10 on the large-diameter side of the rollers 4, 4a and the inside surface 11 in the axial direction of the large-diameter side flange section 8.
In the rotation support unit in which the tapered roller bearing 1, 1a is assembled, there is no particular problem as long as a sufficient amount of lubrication oil is supplied. However, regardless of the type of rotation support unit in which the tapered roller bearing 1, 1a is assembled, it is not possible to completely rule out the possibility that due to some kind of trouble or faulty maintenance, the lubrication oil that is supplied to the tapered roller bearing 1, 1a will become insufficient or dried up. In the case where the lubrication oil that is supplied to the tapered roller bearing 1, 1a becomes insufficient or dried up, first, the wear of the sliding surfaces with the most severe condition of the end surfaces 10 on the large-diameter side of the rollers and the inside surface 11 in the axial direction of the large-diameter side flange section 8 advances considerably. Furthermore, in a severe case, the end surfaces 10 on the large-diameter side of the rollers 4, 4a and the inside surface 11 in the axial direction of the large-diameter side flange section 8 will stick, and it will become impossible for the tapered rollers 4, 4a to rotate and revolve, and furthermore, the rolling surfaces of these tapered rollers 4, 4a and the outer raceway 6 will stick, and it will become impossible for the outer ring 2 to rotate relative to the inner ring 3, causing so called seizure to occur.
When this kind of seizure occurs, normal operation of the vehicle (railroad car, automobile or the like) as well as moving the vehicle becomes difficult, and it becomes easy for problems to occur such as delays in restoring the railroad, causing traffic jams and the like. When it becomes impossible for the rotation support unit to turn, this may cause trouble to occur in other parts, and it becomes easy for problems to occur that require much money and time to repair.
As illustrated in the third example of conventional construction in FIG. 39, such problems easily occur in the case of a tapered roller bearing 1b having a large contact angle, or in other words, when the contact angle with respect to the center axis of the outer raceway 6a that is formed around the inner circumferential surface of the outer ring 2a and the inner raceway 7a that is formed around the outer circumferential surface of the inner ring 3a is large, and when the angle of inclination between the axis of rotation of the tapered rollers 4a and the center axis of the outer ring 2a and inner ring 3a is large. For example, in the case of a tapered roller bearing 1b having a contact angle that is 20° or more, the component force that causes the rollers 4a to displace toward the large diameter side due to a large load (radial load and thrust load) that is applied during operation becomes large, and thus the contact pressure in the area of sliding between the end surfaces 10 on the large-diameter side of the tapered rollers 4a and the inside surface 11 in the axial direction of the large-diameter side flange section 8 that is formed around the outer circumferential surface on the end section of the inner ring 3a becomes large. As a result, the lubrication state becomes insufficient, and it becomes easy for severe wear to occur at the areas of sliding contact between these surfaces 10, 11. Particularly, when the contact angle is 25° or more, this tendency appears even more.
In the case of the retainer 5b that is assembled in the tapered roller bearing 1b having a large contact angle as illustrated in FIG. 39, the difference between the diameter of the large-diameter side rim section 12b and the diameter of the small-diameter side rim section 13b is large as illustrated in FIG. 40 to FIG. 41, and the angle of inclination of the column sections 14b that span between these rim sections 12b, 13b is large.
When the retainer 5a that is illustrated in FIG. 37 and FIG. 38, or the retainer 5b that is illustrated in FIG. 39 is manufactured using synthetic resin, a die 24 apparatus that comprises a pair of dies 22, 23 that move close or far from each other in the axial direction as illustrated in FIG. 42 is used, and the retainer is formed by injection molding by performing so-called axial drawing. In other words, with these dies 22, 23 facing each other, pressure is applied to thermoplastic synthetic resin, which is in a heated and molten state, and fed through a plurality of feed holes called gates into the formation space (cavity) that is formed between these dies 22, 23. Then, after the synthetic resin has cooled and hardened, the dies 22, 23 are separated and the formed retainer 5b (5a) is removed.
As described above, in a tapered roller bearing 1, 1a, 1b that uses any one of the retainers 5, 5a, 5b having the construction described above, there is a possibility that significant wear or seizure will occur. In consideration of the situation described above, JP2007-40512(A) and JP2007-270851(A) disclose construction wherein a small amount of lubrication oil is used effectively to lubricate the areas of sliding contact between the end surfaces on the large-diameter side of the tapered rollers and the inside surface in the axial direction of the large-diameter side flange section. FIG. 43 to FIG. 45 illustrate two examples of the conventional construction disclosed in JP2007-40512(A).
First, in the case of the fourth example of conventional construction illustrated in FIG. 43, an oil retaining section 17 is formed all the way around the circumference on the end section of the large-diameter side of the inner circumferential surface of the retainer 5c by bending the end section on the large-diameter side of the retainer 5c made of metal plate inward in the radial direction. In this fourth example of conventional construction, lubrication oil that is stored in the oil retaining section 17 is supplied to the areas of sliding contact between the end surfaces 10 on the large-diameter side of the tapered rollers 4 and the inside surface in the axial direction of the large-diameter side flange section 8 in order to suppress wear when lubrication becomes insufficient.
Next, in the case of a fifth example of conventional construction illustrated in FIG. 44 and FIG. 45, an oil retaining section 17a is formed on the end section on the small-diameter side of the outer circumferential surface of the retainer 5d by bending the end section on the small-diameter side of the retainer 5d outward in the radial direction. A plurality of partition plates 18 divide this oil retaining section 17a into a plurality of sections in the circumferential direction. In this fifth example of conventional construction, lubrication oil that adheres to the outer circumferential surface of the retainer 5d and that has reached the small-diameter end section of this retainer 5d is prevented from flowing away, and this lubrication oil is supplied to the areas of sliding contact between the end surfaces 10 on the large-diameter side of the tapered rollers 4 and the inside surface 11 in the axial direction of the large-diameter flange section 8, suppressing wear when lubrication becomes insufficient.
In the two examples of conventional construction described above, even though durability is improved when compared with the first through third examples of conventional construction, it is not always possible to efficiently supply a small amount of lubrication oil to the areas of contact between the end surfaces 10 on the large-diameter side of the rollers 4 and the inside surface 11 in the axial direction, and thus effective use of the small amount of oil is not sufficiently achieved. For example, in the case of the fourth example of conventional construction illustrated in FIG. 43, with oil accumulated as is in the oil retaining section 17, the amount of lubrication oil that does not adhere to the end surfaces 10 on the large-diameter side of the tapered rollers 4 increases, and thus it becomes difficult to effectively use the small amount of remaining lubrication oil. Moreover, in the case of the fifth example of conventional construction illustrated in FIG. 44 and FIG. 45, the oil retaining section 17a is formed in a part that is greatly separated from the areas of contact between the end surfaces 10 on the large-diameter side and the inside surface 11 in the axial direction, so it is difficult to effectively use the small amount of lubrication oil for lubricating these areas of contact. This aspect of not being able to effectively use the small amount of lubrication oil to lubricate the areas of contact between the end surfaces 10 on the large-diameter side and the inside surface 11 in the axial direction is the same even when these forms of conventional construction are combined and a plurality of partition plates 18 as illustrated in FIG. 45 are provided on the oil retaining unit 17 that is illustrated in FIG. 43.
JP2007-270851(A) discloses construction wherein lubrication oil that is guided over the inner circumferential surface of the retainer is guided to the area of sliding contact between the end surfaces on the large-diameter side of the tapered rollers and the inside surface in the axial direction of the large-diameter side flange section by way of a large-diameter side flange that faces inward and is provided on the edge section on the end of the large-diameter side of the retainer. In the case of construction such as disclosed in JP2007-270851(A) as well, even though it is possible to improve durability more than in the case of the first through third examples of conventional construction, from the aspect of efficiently supplying a small amount of lubrication oil to the areas of sliding contact between the end surfaces on the large-diameter side and inside surface in the axial direction, there is still room for improvement.